NOVEL LOW-ENERGY NEUTRAL ATOM IMAGING TECHNIQUE

Recently proposed low-energy neutral atom (LENA) imaging techniques re ly on collisional processes to convert LENAs into ions to separate the neutrals from the intense UV radiation background. At low energies, t hese collisional processes have poor conversion efficiencies and limit the angular resolution of these devices. However, if the intense UV l ight background can be suppressed, direct LENA detection is possible. We present results from a series of experiments designed to develop a novel filtering structure based on free-standing gold transmission gra tings. If the grating period is sufficiently small, the gratings can s ubstantially polarize UV light in the wavelength range 300 to 1500 Ang strom. If a second grating is placed behind the first grating with its axis of polarization oriented perpendicular to that of the first, con siderable attenuation of the UV radiation is achievable. The neutrals pass through the remaining open area of two gratings and are directly detected. We have obtained nominal 2000-Angstrom-period (1000-Angstrom bars with 1000-Angstrom, slits) gratings and measured their UV and at omic transmission characteristics. The geometric factor of a LENA imag er based on this technology is comparable to that of other proposed LE NA imagers, with a significantly better angular resolution.